287
FXUS65 KGJT 232041
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
241 PM MDT Thu May 23 2024

.KEY MESSAGES...

- A cold front will be bring scattered showers and potentially a
  thunderstorm or two to the central northern Colorado mountains
  late this afternoon and evening.

- Widespread gusty winds of 30 to 40 mph will diminish this
  evening.

- Another storm blows through on Saturday bringing the
  likelihood for showers and mountain snow to all but extreme
  southeast Utah and southwest Colorado with the norther half of
  the forecast area favored.

- Temperatures become much warmer early next week.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 241 PM MDT Thu May 23 2024

The cold front driven southward by the latest trough to impact
the forecast area was just south of the I-70 corridor as of 20Z
this afternoon. Strong, gusty southwest winds ahead of the front
ranged from 15 to 25 mph with occasional gusts to 40, and as
high as 48 mph. Meanwhile, north of the front light showers were
ongoing over a portion of the northwest Colorado plateau and the
Elkhead and northern Park mountains.

The trough is expected to continue to shift east this evening
and as a result, showers will continue over the northern
mountains and Steamboat basin while spreading into the central
Colorado mountains. Snowfall at higher elevations is expected to
be relatively light with accumulations by Friday morning only
amounting to an inch or two above treeline. Since the trough
axis will shift east of the Continental Divide early this
evening the resultant subsidence in it wake will cause showers
to diminish by midnight with dry conditions and clearing during
the remainder of the night.

A low amplitude transitory ridge moves over the area on Friday
as the next trough moves over the Great Basin later in the day.
Modest moisture in the 700-500 mb layer will generate increased
clouds over the area, mainly in the afternoon over the northern
portion of the forecast area. However, the dryness indicated in
the subcloud layer is likely to inhibit showers from occurring,
though virga is likely. Winds will be significantly reduced
below the ridge, largely hold to normal diurnal patterns.

As the axis of the Great Basin trough shifts to the western
border of Utah late Friday night jet divergence and overrunning
southwest flow is expected to generate scattered showers over
northeast Utah and northwest Colorado with only slight chances
along the I-70 corridor with little to no chance south of there.

Temperatures will continue to run a bit below normal during the
period, though that`s not an entirely bad thing.


&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 241 PM MDT Thu May 23 2024

The next wave drags across the CWA on Saturday, ramping up another
round of afternoon showers and thunderstorms. The cold(er) pool
associated with this trough won`t dig much further south than the
northern aspect of the San Juan`s, so the Four Corners region
doesn`t appear to see much in terms of moisture or a temperature
gradient in the front`s wake. However, best PVA, source of lift and
instability will be focused along and north of the I-70 corridor by
mid afternoon. As such, stronger potential for thunderstorms and
bursts of heavy rain drifting off mountainous terrain appear to be
over counties north of Mesa and Pitkin in western CO. This quick
moving system lifts east of the Divide Sunday night with dry
northwest flow invading the Western Slope through the end of the
weekend. Ridging builds along the spine of the Rockies on Memorial
Day, which returns a warming trend for eastern Utah and western
Colorado. Forecast guidance is consistent across the board of
ensembles with maximum heights straddled overhead through Tuesday.
The southern extent of the next PacNW trough varies by days 6 and 7,
though consensus remains consistent that southwest winds dominate
flow aloft by the end of the forecast period. As a result, 90 degree
weather filters back into the region early next week, reaching the
Grand Valley by mid week. Readings across the board run about 5 to 8
degrees above normal for the end of May, and extended guidance
doesn`t show a relief from this warm pool even as we head into June.

Snowmelt will ramp back up in response to next week`s warming trend,
so we expect to see river stage and flows gradually rising in
sequence. Higher terrain across the upper Gunnison, Colorado
Headwaters and Yampa River basins are still sitting at, or just
above normal in terms of snowpack. Therefore, seasonal peaks in flow
could be just around the corner if this prolong period of warm and
dry weather persists. Fortunately, probability remains low for
flooding this runoff season.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1136 AM MDT Thu May 23 2024

Today`s cold front is nosing into the northwest corner of the
forecast area. High clouds ahead of the boundary are quickly
filling in ahead, covering areas generally north of the I-70
corridor. Expect gusty southwest winds along and ahead of said
front, with max gusts exceeding 30 kts over most TAF sites
this afternoon. Precipitation looks weak with this one, so most
TAF sites can expect gusty outflow winds from decaying storms
near by and/or virga overhead rather than lowered CIGS/VIS.
Chance for thunderstorms favors the high country along and,
generally, north of CNY- MTJ- and GUC through late evening
hours. However, storms are expected to weaken by sunset and the
frontal boundary will quickly drift east of the Divide
overnight. Mostly clear skies and VFR conditions are forecast
for Friday.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...NL
LONG TERM...ERW
AVIATION...TGJT